ARL - my part in its demise, or

Warspite moored on static noise range
HMS/M WARSPITE on Loch Fyne - Inveraray beyond

ARL-style fun & games plus 'odd' anecdotes

I finished full-time education at Polytechnic in June 1963. By then I had decided on a technical career and left it to my results in the subjects of Physics and Chemistry to determine which particular discipline - I got the same grade in both!!!!! In response to an advert in the Surrey Comet I applied to ARL and was accepted as a Scientific Assistant. {anecdote}

I almost didn't make the interview as I and my father who had lived in Teddington for virtually all his life, were only aware of the Upper Lodge site and so I duly reported there. The guard on the gate was extremely helpful and arranged transport to the main site in Queens Road, where I was to be interviewed; I, therefore, arrived in grand style in the Superintendent's car. It could only be (all) downhill from there!

I assumed that I would be working in C Group having expressed an interest in Chemistry at the interview; to be honest, it was only what I was told about the work of C Group that I understood. I was therefore a little surprised and a tad disappointed on Monday 7th October 1963 (my first day) to be escorted to the office of Dr AGD Watson (L Group Leader at that time) where he informed me I'd be working on submarine sonar. I was exceedingly fortunate to have had Ron Morris as my first boss, he really fired my enthusiasm for electronics and sonar. I now know how leading edge stuff it was. At the time it was just a very interesting job that gave me the opportunity to build bigger and better, valve and transistor amps for my guitar!


My first job at ARL was assisting with the maintenance and operation of a 1000-valve piece of equipment called DICE. The name DICE came from Digital Correlation Equipment, a rather loose description of its purpose to generate (in real-time) a bearing versus time display for a ship or submarine, utilising their broadband, in-water, radiated noise / sound. In my days DICE was taken as standing for Digital Integrated Correlation Equipment. In its original form (in the mid-1950s) it was simply known as the (digital) Acoustics Research Computer for Broadband passive (Sonar) signal processing. This specially developed equipment was designed to provide correlation of the signals from a pair of hydrophones selected from arrays of hydrophones deployed on the seabed, and was successfully used for operational assessment of the Corsair Project. The following photos, taken 1960-1, show the much increased capability DICE II, which could compute 200 cross-correlations for up to 12 input channels. <fuller description> By the time I joined in 1963, DICE II had reached its final form, having been modified further. The number of (Teledeltos) electro-sensitive paper recorders was reduced to three. The consequential reduction in size of the output console, the conversion to sliding-door access to the room, and the relocation of the Bryan-Savage 1kw power amplifier (left-hand end of output console in the photo) to the opposite corner of the room, provided room for two six-foot racks containing a high precision, 16-channel, analogue (DR) tape recorder and replay amplifiers produced by the Epsilon Company of St Margarets. There was also a slightly lower spec 'portable' version made by the same Company. {anecdotes}

Re: Bryan-Savage 1kw power amplifier. For fault finding on DICE, there was two Cathode Ray Oscilloscopes (CRO) made by EMI. The input signal connection was achieved by a pair of crocodile clips on the end of a length of coax cable plugged into the CRO. Some croc clips had insulation to protect the user, the ones I used on the occasion I needed to check the input signal to the amplifier, didn't! In there infinite wisdom, the designers of the amplifier provided a test-point for the High Tension (HT) voltage for the power output stage on the next tag, of a tag-strip, to the signal input connection. The tag-strip was accessed from the rear of the 6-ft cabinet, and it was high-up near the front. The only way yours truly could reach it was by balancing with my insteps on the surround along the bottom of the cabinet. Carefully trying to maintain my balance, I gingerly extended the signal input croc-clip held open between finger and thumb of my right hand. With my balance going critical I, unerringly, made contact with the HT test-point. Working with valve equipment one becomes quite blasé about receiving the odd 'packet' of anything up to 300 volts DC, but 850 volts DC packs a mighty punch! My back was slammed against the wall, some 18 inches away, knocking most of the breath out of me. Quite fortunately, although my head hit the wall, my shoulder blades took the majority of the force. The next thing I can clearly recall was the sound of our Tea-lady Bennie with her trolley, so I walked a little unsteadily into the adjoining lab to retrieve my tea-mug. Picking-up my mug I discovered that my right hand was virtually numb. Undaunted I got my afternoon tea together with (I felt I deserved) a pre-packed slice of fruit-cake, and took them along the corridor to the (small) workshop to relate the episode to Tom the Wireman. Tom, upon hearing the tale, took a deep drag of his cigarette and duly pronounced me 'quite high resistance'!

Re: Epsilon 16-channel portable tape recorder. This being a domestically-produced, although special order, tape recorder it required 240 volt AC mains power. With the completion of the fit of prototype Sonar 2007 (i.e. SOAP) in HMS/M Otus there was a need for a check-out prior to the forthcoming (crucial) sea-trial. It was decided that the tape recorder and (its separate) replay unit could be run onboard from the sub's 110 volt supply via a step-down transformer working the other way round. We had a Rolls-Royce step-down (240 volt in, 120 volt out) transformer enclosed in a NU-metal case, which appeared man enough for the job. So off we (Ron and I) set for HMS Dolphin with the tape recorder plus replay unit and Ron's gear, for the trial, squidged into my Mini. The first challenge was to get the tape recorder and its replay unit down the forward accommodation hatch of Otus, being extremely heavy the fact that it just fitted didn't help much. It was quite a struggle. There was little space left in the Sound Room, so we set-up the tape recorder, replay unit and transformer in the Captain's Cabin, directly across the passageway from the Sound Room. With the tape playing back and satisfactory output from SOAP, we adjourned to the fish & chip shop in Gosport. We arrived back onboard Otus to a faint smell of singeing, but nobody appeared alarmed. In fact, we didn't meet anybody, which was just as well. Our super-duper transformer did its best at powering the tape recorder and replay unit, but got rather hot in the process. The lack of space, onboard, meant we'd placed the tape recorder, etc. on the Captain's bunk, and the transformer had scorched an impression of itself into the sleeping-bag! Contrary to gravity, the tape recorder, etc. came-off the submarine a lot quicker than we'd struggled to get it on. As a parting gesture, I placed the Captain's cap, that was hanging on the hook on the back of his cabin-door, over the scorched area of his sleeping-bag. I drove back to Teddington in the dead of night leaving Ron to do the explaining!

Right: Some of the 6 cabinets housing the valve-based digital processing. Left: Output Console with six Teledeltos recorders, also the 1kw power amplifier

In the above left-hand photo, Steve Sutton is shown handling one of the many plug-in modules which were used for the bulk of the digital circuits of DICE. The cabinet being accessed contained DICE's storage units: electro-mechanical, short-term delay lines (the upper, tall units in the photo) and a magnetic drum storage unit (bottom of cabinet), these were at the heart of the DICE's cross-correlation processing and integration. A further modification of DICE II was the relocation of the switches (shown in the above photograph) from the panel, which faced the output console, to inside the cabinet. This was obviously felt necessary to limit the vulnerability to the 'Phantom Knob Twiddler', as these switches controlled the whole operation of DICE's processing other than the selection of which channels from the tape recorder were fed (via octave band-pass filter units) into DICE's input channel.

The above right-hand photo of the Output Console area shows a total compliment of six Teledeltos recorders. These were analogue recorders where the voltage applied to the stylus, as it passed across the paper, left a proportionally dark mark - bigger the voltage, darker the mark, up to a max of some 350 volts. The recorders were synchronised to DICE's operating cycle by virtue of their AC motors driving the stylus and advancing the paper. Thus, they displayed the result of the 200 cross-correlations as relative bearings over 180 degrees ( typically forward-broadside-aft, for flank arrays) across the paper; time / history axis being down the paper. As stated earlier, by the time I joined, decisions must have been taken as to the optimum style of processing to be displayed, and as a consequence the number of Teledeltos recorders was reduced to three. {anecdotes}

Fuse-changing packets - every now and again the fuse on the high voltage supply to the Write Amplifiers of the Teledeltos recorders would blow at switch-on. Rather than going through the rather laborious process of powering everything down again, I chose to change the fuse with the power on. The fuse holder on the rear of the Output Console although (in theory) completely insulated took delight in giving me quite a nasty electric shock. I tried various techniques to avoid the electric shock when inserting new fuses, but never found one that worked satisfactorily - some packets seemed less severe but I could have been extra high resistance on those occasions.

Teledeltos Recorder Paper Marking. It appeared as something of an after-thought that a chemical analysis was performed on the fumes from the Teledeltos Recorder. The fumes resulted from the marking process, which was (for all intents and purposes) a partial burning of the chemical-dosed, and so, electro-sensitive paper, arising from the (large) voltage on the stylus. The results of the chemical analysis (performed on-site at ARL by a doctor from AML) showed the fumes to be pretty toxic. In fact, he was appalled! Quite fortuitously, the heat generated by all the valves in DICE meant the windows were open most of the time. As it was, headaches were quite commonplace after a session of mechanically aligning the three styli of each recorder; a jeweller's screwdriver was used to adjust each stylus, in turn, such that a continuous line was marked as the paper was drawn through the recorder. In a bit of a rush an alternative paper was needed that could be used on-board a submarine i.e. one that didn't generate toxic fumes. The original (toxic) type of paper was chosen for its quality of marking; others had been tried, in the past, and found to be unsatisfactory. As luck would have it, a company called Sensitised Coatings of Forest Row had been addressing the problem and were able to supply a highly satisfactory replacement. The, what became the standard, paper (non-toxic fumes) was whiter in colour providing greater contrast, and marked with comparable quality at much lower voltages - max black at 150 volts. Another important (operational) bonus was that markings on the new paper were much easier to see under red lighting conditions; somewhat ironically my Section Leader, Ray Coghlan was involved in the adoption of red lighting to aid night-sight adaptation, onboard ships and submarines, earlier in his career.

One of DICE's plug-in module.

The above photo is of a Shift Register module of which there were many in DICE. The circuit design employed Mullard's state-of-the-art, high-speed switching valve: E88CC - note the departure from Mullard's convention used for other Double Triodes e.g. ECC83. Shift Registers are a key feature of digital processing as they allow ordered events to be (momentarily) frozen in time for computations. Cascaded (transistorised) Shift Register modules were used in SOAP (see below) to provide the (equivalent) difference in time of arrival of the in-water, acoustic wave-front (between a pair of hydrophones) to be correlated for 200 possible bearings, over the 180 degrees of cover of a line array of hydrophones. Both DICE and SOAP provided for up to eight separate correlations (for the same bearing, but employing a different pair of hydrophones) and these were integrated together to yield a significant (processing) gain.

Project DICE was kept so much under wraps that staff working in the same hut (on other projects) had very little idea of what it was all about – asking questions was simply not the done thing! Further, casual visitors were, to an extent, not welcome in the hut. Indeed in 1964, I received a verbal rocket for inviting friends Ray Wood and Tony Hughes, from NPL, into the DICE lab in Orlit Hut at ARL. Fortuitously, both were involved in work at NPL that required staff to sign the “Official Secrets Act” non-disclosure. I did, as a matter of fact, have an excuse as the standing orders for ARL, which I’d read recently, allowed for NPL staff to enter the establishment. The wording of this open statement was hurriedly changed, following their visit, to ‘NPL staff may pass through the grounds of the establishment on production of their passes’. ARL was, after all, a class “A” security, military establishment with the greater proportion of work at that time either Secret, or Secret Atomic - a variation on Top Secret for the ARL work related to the radiated noise from nuclear submarines and their stealth capability.

By the time I joined, a project to produce the equivalent correlation processing of DICE II in a transistorised form, small enough to fit in a submarine, was running in parallel. This project went by the name of SOAP, which was not an acronym, although Submarine Onboard Array (digital) Processing could have been a likely contender!? Initially, the concept was proven by a contract placed with BAC at Stevenage, selected for their 'state-of-the-art' knowledge of transistor circuit design.



I left on 31st Dec 1973, but had several meetings there in 1986-7. On one occasion the chap I was visiting was surprised that I knew his internal telephone number - he was, after all, the latest occupant of the desk that I vacated some 13 years earlier!